Helical spring type connector



Oct. 5, 1965 R. H. JOHNS HELICAL SPRING TYPE CONNECTOR Filed 001:. 29,1962 lNVENTR United States Patent 3,219,722 HELKCAL SPRING TYPECUNNECTOR Robert H. Johns, 815 Fetters Mill Road, Bryn Athyn, Pa. FiledGet. 29, 1962, bier. No. 233,729 7 Claims. ((31. 339256) This inventionrelates to what the name implies, a helically coiled spring of the typethat has long been serving as a quickly attachable and detachablesolderless electrical connector. An object is to provide a device ofthis sort which is capable of more firmly holding a wire inserted andmoved transversely between the convultions of such a coil and lesslikely to be accidentally ejected. Another object is to provideSimultaneously with the foregoing, a coil which may be easily grasped,with less danger of the fingers slipping. Still another object is toprovide a support for such a coil, by means of which it may beconveniently mounted in an upright position in a perforated board,especially when the perforations are not of precisely the same diameter.

A helix of spring metal is said to be an early type of solderlesselectrical connector. During its long existence it has not beensatisfactory because of a tendency for the clamping portions of theconvolutions to function as inclined planes with a component of theclamping pressure tending to expel an inserted wire extendingtransversely of the axis of the helix. Now this tendency has beeneliminated and the inserted wire is now held in position as soon as thetransverse conductor has been moved past the axis of the helix with notendency to be expelled as was the case before.

According to this invention each convolution of the spring helix hasstraight sides and approximates a polygon, preferably with four sides.An inserted wire may now be pushed transversely into the new coil toabut one of the sides of a quadrilateral convolution as a stop. As longas the inserted wire is pushed into the coil to a position beyond thelongitudinal axis of the coil, there will be no tendency for it to beexpelled.

Referring to the drawing,

FIG. 1 is a side view through one embodiment of this invention insertedin a perforated plate.

FIG. 2 is a top plan view of a coil of FIG. 1 type without a supportingplate.

FIG. 3 illustrates a wire inserted in the upper convolutions of a coilof FIG. 1 type before it has been moved past the coil axis.

FIG. 4 shows the wire fully inserted into the convolutions of FIG. 3.

FIG. 5 is a top plan view of the inserted wire and coil of FIG. 4 turned90.

The coil in FIG. 1 comprises an upper portion of approximately polygonalconvolutions and a lower portion 11 formed of circular convolutions ofdecreasing diameters, inserted in a perforation 12 in a plate orfoundation 13. A timed steel music wire has been found suitable for theportions 1% and 11. To obtain the bends having a permanent set for theupper polygonal convolutions, the angles are formed by winding the wiretightly on a mandrel whose cross-section is an equilateral triangle.

The lower portion 11 in FIG. 1 is tapered to facilitate this lowerportion expansively clamping the coil within a circular recess 12. Toeffect such clamping the coil is pushed and turned or twisted into thehole 12 in a direction tending to reduce the diameters of the taperedcircular convolutions. Friction between the recess 12 and the lowerportion of the spring tends to wind the tapered convolutions tighter andreduce their diameters, permitting the lower portion 11 to penetratedeeper into the hole 12. Then on cessation of the torque the taperedlayers expand against the walls of the perforation to hold the entirecoil in its upstanding position normal to the plane of the plate 13. Toemploy a clockwise twist for inserting the connector into a perforation,the spring coil is wound such that the direction of the spiral is thesame as that of a left hand thread. A connector is removed from aperforation in plate 13 by imparting a torque in the same direction asthat used in inserting it, which also tends to reduce the diameter ofthe lower tapered portion and free it from the perforation.

By virtue of the length of contact between the convolutions of the lowerportion of the spring and the walls of the perforation, and the uniformexpansive force between them, the tapered lower portion of the springaffords a secure mounting device for the electrical connector upperportion.

The relative diameters for the wire size and for the inserted or clampedWire in FIGS. 3 to 5 are only examples.

In FIG. 3 the conductor 14 is clamped between the convolutions 15 and16. A side 17 of the polygonal co-nvolution opposite the place ofentrance of the wire 14 into the helical coil serves as an abutment walllimiting further movement of the conductor transversely of the helix. Anessential feature of the polygonal convolution is that it permits theentry of an inserted wire all the way to the polygon side 17, with theresulting tilt of the longitudinal axis of the connector. This tiltprovides the cramping force that retains the inserted wire in stableequilibrium in the spring. A wire inserted into a conventional spiralspring cannot penetrate to such a depth without permanently deformingthe spring, since the length of the spring element to which a torsionalstress of the spring is chiefly confined becomes shorter as the insertedwire is pushed farther into the helix. The stress of any spiral orhelical spring is applied to an element of the spring or are of aconvolution as a torsional stress. As an inserted trans verse wirepasses the longitudinal axis of a helical spring of circularcross-section and advances farther into the spiral, it must twist thespring open wider, yet at the same time, the length of arc of a circularconvolution to which this greater torsional stress is applied decreases.This increasing torison on a decreasing length of arc will twist thespring material past its elastic limit in torsion if an inserted wire ispressed transversely through the spiral spring against the oppositeside. In the present invention each convolution of the spring is apolygon. The torsional stress exerted on the spring when a wire isinserted transversely into the spring is distributed throughout theentire length of the polygon side 17. This allows. the inserted wire tobe pushed to a position against side 17 as an abutment without buildingup prohibitively large torsional stresses in the spring material. Agripping tendency of the polygonal convolutions upon an inserted wire isproduced by the torsion of polygonal side 17, illustrated in FIGS. 3 and4. The vertical motion of side 17 also imparts a tilt to theconvolutions 15 and 16 below and above the inserted wire, bringingvertices 18 and 19 in FIG. 5 into the gap in the spring as barriersopposing the transverse motion of the inserted wire.

The angle of the vertices between polygon sides is preferably more than60 and less than 90 or about This angle is what causes the vertices ofthe several convolutions to be not aligned longitudinally of the spring.The reason for these angles being substantially uniform and of theapproximate value stated is believed to be due to the 60 bends on thewinding fonn or mandrel, causing a permanent set to occur in the Wirebeing wound after it is removed from the form which has a cross sectionof an equilateral triangle. The aforementioned wire known as music wireor piano wire will give the results described. Other types of springwire will give results with the vertices having some other value morethan 60 and less than 90 but nevertheless capable of causing the severalvertices to be out of alignment longitudinally.

FIGS. 3 to 5 do not show the tapered lower portion for the sake ofsimplicity.

Perhaps a chief advantage of the present invention is the provision of aspring type electrical connector that affords a secure clamp on theconductors attached to it. A second new result is the provision of atapered few circular convolutions constituting a firm support for theelectrical connector above a circular perforation. A third new result isthe formation of the several vertices in nonalignment longitudinally ofthe spring, providing a better finger and thumb grip on the upper coilportion 10. While the convolutions are generally of four sides asillustrated, the terms polygon and quadrilateral are be lievedappropriate although the four sides of a convolution are not strictlyclosed nor coplanar. A feature is believed to be the localization oftorisional stresses to the side functioning as an abutment, an adjacentside at one end being bent upward while that at the opposite end is bentdownward by the inserted wire, resulting in a torsional clamp by theabutment side and its adjacent convolutions.

I claim:

1. The combination with a helical metal spring type connector havingeach of a plurality of its convolutions of polygonal shape and havingmore than three sides for a substantial portion of its axial length, ofan electrical conductor extending through said helical connectorgenerally normal to the axis of said helical connector and contiguous toone of said polygon sides of said connector on an inner side thereofbetween such side and the axis of said connector, whereby on insertionof said conductor between connector convolutions and on relative lateralmovement between said conductor and connector across and beyond the axisof the connector, the conductor is held more securely within theconnector than would be the case were the connector convolutions ofcircular shape or were the conductor not moved laterally well past saidaxis of said helical connector.

2. In a process for moving an elongated substantially straightelectrical conductor transversely of itself between polygonalconvolutions of a helical spring connector of electrically conductivemetal wire of generally circular cross section, the combinationtherewith of the improvement for enhancing the clamping force of theconvolutions contiguous said conductor on the conductor, saidimprovement comprising transversely moving said conductor past the axisof said connector and toward a side of said connector substantiallyopposite the place of entry of said conductor into said connectorwhereby the contiguous and other convolutions slope in a convergingdirection toward the place of entry of the conductor into the connectorafter said conductor has moved past said axis.

3. A process according to claim 2 which includes moving said conductortransversely between convolutions until said conductor substantiallyabuts a side of the connector polygon convolution opposite theapproximate location at which the conductor entered said connector.

4. A helical spring type connector having a hollow axial portion acrosswhich an electrical conductor may be moved when inserted betweenadjacent coaxial convolutions of the helical spring, said springconnector containing the improvement for better holding at least onesuch conductor against coming out of the connector accidentally bymovement of the conductor laterally, said improvement comprising atleast three generally similar bends in each convolution whereby eachsuch convolution is of polygonal shape and is adapted to have any one ofits generally straight sides to constitute an abutment on its inner sidefor a conductor inserted laterally of itself and the connector and movedpast the axis of said connector when said abutment side gets under atorsional stress due to one convolution side adjacent to the abutmentside passing under and the other adjacent convolu tion side passing oversaid conductor.

5. A helical spring type connector according to claim 4 havingconvolutions of generally quadrilateral shape with the vertex anglebetween each pair of adjacent sides being of more than 60 and less than6. A connector according to claim 4 in which said connector is securedto a generally flat plate with the helical connector axis upstanding andgenerally normal to said plate.

7. A helical connector according to claim d in which each convolution isof general quadrilateral shape except in an end portion of saidconnector having circular convolutions which are tapered about 5 to aprojected axis of said connector whereby the tapered end portion may beinserted in a generally cylindrical perforation of a plate and rotatedin a direction tending to reduce the diameter of at least one of thetapered circular convolutions when friction tends to wind the taperedconvolutions tighter within the walls of said perforation.

References Cited by the Examiner UNITED STATES PATENTS 317,887 5/85Thompson 339256 640,479 1/00 Mills 339--254 1,225,630 5/17 Hicks.1,780,826 11/30 Kuhn 339112 1,946,889 2/34 Wessel. 2,124,461 7/38Challet 33925 6 2,216,201 10/40 Keller 29155.55 2,473,570 6/49Chirelstein 29155.55 2,957,218 10/60 Sponsel 24-66 FOREIGN PATENTS111,126 11/17 Great Britain.

OTHER REFERENCES Unusual Uses for Helical Wire Springs, from ProductEng. Design Manual, 1959, pages 328 and 329 (page 329 only relied upon).

JOSEPH D. SEEKS, Primary Examiner.

4. A HELICAL SPRING TYPE CONNECTOR HAVING A HOLLOW AXIAL PORTION ACROSSWHICH AN ELECTRICAL CONDUCTOR MAY BE MOVED WHEN INSERTED BETWEENADJACENT COAXIAL CONVOLUTIONS OF THE HELICAL SPRING, SAID SPRINGCONNECTOR CONTAINING THE IMPROVEMENT FOR BETTER HOLDING AT LEAST ONESUCH CONDUCTOR AGAINST COMING OUT OF THE CONNECTOR ACCIDENTALLY BYMOVEMENT OF THE CONDUCTOR LATERALLY, SAID IMPROVEMENT COMPRISING ATLEAST THREE GENERALLY SIMILAR BENDS IN EACH CONVOLUTION WHEREBY EACHSUCH CONVOLUTION IS OF POLYGONAL SHAPE AND IS ADAPTED TO HAVE ANY ONE OFITS GENERALLY STRAIGHT SIDES TO CONSTITUTE AN ABUTMENT ON ITS INNER SIDEFOR A CONDUCTOR INSERTED LATERALLY OF ITSELF AND THE CONNECTOR AND MOVEDPAST THE AXIS OF SAID CONNECTOR WHEN SAID ABUTMENT SIDE GETS UNDER ATORSIONAL STRESS DUE TO ONE CONVOLUTION SIDE ADJACENT TO THE ABUTMENTSIDE PASSING UNDER AND THE OTHER ADJACENT CONVOLUTION SIDE PASSING OVERSAID CONDUCTOR.